Calcium is vital to normal bone formation and maintenance of bone density. Long-term dietary calcium insufficiency almost always results in net loss of calcium from the bones. The U.S. recommended daily allowance (RDA) for calcium is 800 mg/day, with an additional 400 mg advisable for pregnant and lactating women. A large proportion of the over-60 population consumes less than one-half of the RDA for calcium. This is also the age group most at risk of developing osteoporosis, which is characterized by loss of the organic matrix as well as progressive demineralization of the bone. Some studies suggest that postmenopausal women may need up to 1,200 mg calcium/day just to maintain calcium balance (Textbook of Biochemistry With Clinical Correlations, Second Edition, T. Devlin, Ed., John Wiley & Sons, New York, 1986, pp. 983-984).
Calcium has also been demonstrated to have an antihypertensive effect (McCarron, Am. J. Clin. Nutr. 65(suppl.):712S-716S, 1997). Calcium is also required for many enzymes, mediates some hormonal responses, and is essential for muscle contractility and normal neuromuscular irritability.
Taurine is an amino acid present in high concentrations in excitable and secretory tissue. Its role in cardiac function has received particular attention (Huxtable, Physiol. Rev., 72:101-163, 1992; Schaffer et al., Taurine in Health and Disease, pp. 171-180, 1994). Although taurine can be synthesized endogenously from the amino acid cysteine, in mammals it is derived principally from the diet and is thus considered a "conditionally essential" nutrient. Conventional diets supply 40-400 mg of taurine daily, while vegetarian diets are extremely low in this amino acid.
The main function of taurine in mammals appears to be the regulation of transmembrane ionic movements, especially the regulation of calcium distribution (Schaffer et al., supra.; Huxtable, supra.; Schaffer et al., Taurine: functional Neurochemistry, Physiology and Cardiology, pp. 217-225, 1990). However, the mechanisms of this regulation are not well understood. Taurine has also been shown to have antihypertensive properties (Fujita et al., Circulation 75:525-532, 1987; Inoue et al., Cardiovascular Res., 22:351-358, 1988). Taurine also exerts a platelet stabilizing effect both in vitro and, after oral administration, ex vivo (Hayes et al., Am. J. Clin. Nutr., 49:1211-1216, 1989; Atahanov, Arzneim-Forsch/Drug Res., 42:1311-1313, 1992). Acute intravenous administration of taurine reduces the incidence of arrythmias in animals treated with arrhythmogenic agents and multi-gram doses have been shown to be effective in the treatment of ischemic congestive heart failure (Azuma et al., Curr Ther. Res., 34:543-557, 1983). Thus, increased taurine intake appears to be beneficial to vascular health.
Many sources of calcium, including calcium carbonate and calcium citrate, have less than optimal bioavailability. In addition, these sources of calcium require require an acidic environment for calcium release. Ordinarily, this does not present a problem. However, in individuals with achlorohydria, a condition in which stomach acid cannot be produced, these sources of calcium have very poor bioavailability because calcium ions cannot be released from the compounds. The present invention provides a calcium taurate complex for use as a dietary calcium supplement and antihypertensive agent. This complex has excellent calcium bioavailability and does not require an acidic environment for calcium release.